Control apparatus



Nov. 15, 1 949 A. w. PLENSLER 2,488,099

CONTROL APPARATU 5 Filed March 2, 1946 2 Sheets-Sheet l JIM;

INVENTOR. 7

Nov. 15, 1949 w, PLENSLER 2,488,099

CONTROL APPARATUS Filed March 2, 1946 2 Sheets-Sheet 2 16d \J30- J6 INVENTOR. QZezanarZfll lensler;

Patented Nov. 15, 1949 2388,09!)

. UNITED- STATES PATENT OFFICE CONTROL APPARATUS Alexander W. Plensler, Chicago, Ill., assignor to Belmont Radio Corporation, Chicago, 111., a corporation of Illinois Application March 2, 1946, Serial No. 651,636 13 Claims. (01'. 74-1035) 1 2 r The present invention relates to control appa- A still further object of the present invention is ratus for radio receivers and more particularly to to provide a new and improved manually operated manually operable automatic tuners of the meautomatic tuner for radio receivers having a plu chanical type for such receivers. Specifically the rality of control elements on a rotary shaft, with present invention is concerned with an improve- 5 each control element adapted to be set or reset ment on Plensler Patent No. 2,272,922 granted to a predetermined position independently of the February 10, 1942, and assigned to the same asother control elements, and :while maintaining signee as the present application. such other control elements in a fixed position on Many. types of modern radio receivers are prothe rotary shaft.

vided with automatic tuning mechanisms. In Still another object of the present invention is general such automatic tuners comprise a series to provide a new and improved oam' locking of manually actuated push buttons which enable means for an automatic tuner for a radio rethe listener to selectively tune in particular staceiver which comprises friction means for entions merely by pushing or actuating the push gaging a-large area of the tuning shaft.

buttons. In addition the receiver includes man- Further objects and advantages of the present ual means for tuning the receiver to any other invention will become apparent as the following broadcasting station within the range of the redescription proceeds and the features of novelty ceiver, in addition to those for which the autowhich characterize the present invention will be matic tuning arrangement including the push pointed out with particularity in the claims anbuttons is set. In one form of automatic tuner nexed to and forming a part of this specification. for radio receivers -a series of variably positioned For a better understanding of the present incams are provided along the tuning shaft, one for vention reference may be had to the accompanyeach of the push buttons. Suitable cam locking ing drawings in which: 7

means are provided for holding these cams in Fig. 1 is a fragmentary plan view of the tuner their predetermined positions relative to the tunstructure of a radio receiver embodying the presing shaft so that when a push button is actuated, ent invention;

the associated cam is rotated with the consequent Fig. 2 is a sectional view taken along line 2-.2

rotation of the tuning shaft to a predetermined of Fig. 1 but showing the push button in-its deposition corresponding to the particular station pressed position for tuning in a particular stasetting for which the push button and associated "3 tion, but not sufficiently depressed for unlocking cam have been adjusted. In order initially to the cam;

set the automatic tuning arrangement or to Fig. 3 is a side elevational view of one of the change the setting thereof, it is necessary to optuning elements of Fig. 1 taken along line 3--3 erate some means for looking a particular cam of Fig. 2; 1 to the tuning shaft so that relative movement Fig. 4 is an exploded perspective view of the between this cam and the tuning shaft can be tuning mechanism of the present invention;

obtained. The present invention is particularly Fig. 5 is a sectional view taken on line 5 -'5 concerned with a new and improved arrangeof Fig. 1; men for l in h ms to the nin shaf Fig. 6 is a sectional View taken on line 66 of which locking means may be operated in asimple a0 Fig. 5, assuming that Fig. 5 shows a complete manner without additional equipment to afford a structure; and

new setting or adjustment, and so constructed Fig. 7 is also a sectional view taken on line that the unlocking of any particular cam does (-4 of Fig. 5, again assuming that Fig. 5 shows not unlock the other cams. a complete structure.

It is an object of the present invention to pro- Although the present invention is applicable vide anew and improved automatic tuning mechto various forms of automatic tuners for radio anism which is simple and inexpensive to manureceivers it has been illustrated specifically in facture, foolproof in operation and satisfactory the drawings as applied to an automatic .tuner in every respect from the standpoint of the radio of the type disclosed and claimed in the abovelistener who operates the receiver. mentioned Plensler patent.

A further object of the present invention is Referring now to the drawings there is illusto provide a new and improved automatic tuner trated a tuning mechanism for a radio receiver which can be set and reset merely by manipulawhich comprises a rotary shaft In which is suittion of the tuning mechanism itself without the ably journaled in a frame, a portion of which is requirement of extra tools or equipment shgwn at H. The rotary shaft I0 is coupled or otherwise connected to a suitable resonance frequency changing means for tuning the radio receiver to particular stations. In Fig. 1 this resonant frequency changing means is illustrated as a variable condenser I2 having a rotor portion rotatable through an angle of substantially 180, but it should be understood that it might also comprise a variable inductance or the like. Rotation of shaft II! will cause the capacitance of variable condenser I2 to vary with the resultant tuning of the radio set to any desired station within the range of the receiver. To accomplish this a suitable tuning knob, not shown, may be provided in a manner well understood by those skilled in the art.

In accordance with the now well-known automatic mechanical tuning mechanisms "for radio receivers, shaft I is also controllableby a plurality of push buttons or the like whereby particular stations to which the listener frequently desires to listen may be tuned in merely by actuating one of the push buttons which automatically'cau'ses the desired rotation to be imparted to shaft Ill without further effort than to actuate one of the push buttons.

It should be understood that each push button may be associated with a selector unit comprising "a slidable member'which is moved in a generally longitudinal direction upon actuating the push button as is shown in the above-mentioned Plensler patent, or each push button may "be associated with a "selector unit comprising members rotatably'or pivotally mounted on a suitable support. The present invention is ilmsnated in connection with the latter type of selector unit. As illustrated inthe drawings and particularly inFig. '1, two separate selector units 'generally indicated as 'ISaand I3 b have been illustrated, each being provided with a manually actuable push button portion I4. Actually additional selector units and associated push but- "tons could b'e'provided, the number depending upon the number of stations to which the receiver is to be tuned merely by actuating a particular push button. A radio receiver might have as fewas 3 or 4 push buttons or 10 or 12 or more.

The 's'ole'purpose of each individual selector unit i'sfto impart 'a'pre'deterinined rotation to shaft I0, which rotation is "difierent'for eachselector unit. Since each ofthe selector units are identical in every respect only one, namely I3a, will be described hereinafter.

Selector units such as I31; and I3b described in greater detail hereinafter are each adapted to enga'ge" and a'cftuate a cooperating heart-shaped cam 15 to impart different desired station settings'to tuhing'shaft 'IB. Normally each cam I5 is locked or retained against rotation or move- "fnont relativeto tuning" shaft "I U and the present invention is particularly concerned with new and improved looking or clamping means together withsi mple means for locking and unlocking the same, the unlocking mechanism operating only on the particular cam being reset. 7

The selector unit'ISa which is identical with "all the other selector units which may be included'inthe particular radio receiver comprises "a finger actuated lever assembly by means of which the desired setting of cam I5jand, consequently, tuning shaft-I0 mayre'adilybe obtained. This lever assembly comprises a first or actuat- "fng'lver l6 and a second or actuated lever l'l. Lever I7 is provided'with an angularly positioned "notch I8 So thatit maybe slipped over and pivota-Hy mounted on a suitable supporting shaft T9 obvious that some means must be provided to roller 20 is positioned in the low point of the cam periphery,

Lever I1 is preferably pivotally mounted-intermediate the ends thereof so that the end of lever I! not provided with roller 20 extend in a direction toward the associated push button I4.

"Shaft 'IQ also pivotally supports the actuating "lever It which is provided with a notched-out portion 2! for engaging shaft I9. Preferably shaft I9 is provided with reduced diameter portions at the pivot points of levers It and I! for proper positioning thereof or suitable spacers may-be provided on shaft I9 between levers I5 and "I? which would have the same effect. As illustrated, push button I4 is integrally formed with the lever It and is illustrated as a laterally projecting portion thereof. As best shown in Figs. 2and 4 the lever It actually has two integral legs or arms arranged ata substantial angle with respect to each other; a leg Ifia from which push "button 'I leXtends in'a lateral direction and a leg 'ISb which is provided with a pair of resetting prongs 22 and 23. The resetting prong 23, as is best'shown' in Fig. 4, is offset with respect to the mainbo'dy portion of lever I6, and, consequently, alsowithresetting'prong 22. With this arrangement one resetting prong is positioned in a plane parallel to but on one side of cam I5 while the other resetting. prong is positioned in a plane parallel to but on the other side of cam I5.

"Withthe'arrangement described thus far it is impart the forceapplied .to push button It and .lever LIE to actuatedlever Ii, and, consequently, to 0am I5. :As illustrated in the drawings the actuating force is transmitted from lever It to -lever I? through a coiled compression spring 2 5 --having its'ends telescoped over integral projection-portions I60 and I'll) postioned near the innereirids of the two levers IS and II, respectively. "Relative movement between the levers I6 and I? under the influence of spring 25 is limited bya stop portion Iiid projecting laterally from the arm 16a of iever Win the path of movement-of the end of'lever I? which does not support-the roller 26. Preferably stop M3102 is integrally formed with lever IS in the same manner as push button I i.

Assuming for the moment thatcam 'I 5 is rigidly locked to'tuning'shaft I0 and that it is in a position'other 'than'that shown in Fig. 2, depression of pushbutton M will cause clockwise rotation of with respect to tuning shaft Iii may be varied so.

that 'eachpush button may control a desired station through its associated cam it is necessary to provide means for adjusting cam I5 relative to shaft III. One scheme for accomplishing this would betofasten cam IE to shaft It by means of a set screw. This would require the use of a screw driver or wrench or some other tool which is unsatisfactory or the means disclosed in the above cited Plensler patent and the present invention is concerned with a looking or frictional engaging means for locking cam l 5 to shaft II, which means may be released in a simple manner for adjusting the relative positions of cam I5 and shaft I and yet which provides a very large area of frictional engagement, without the intervention of any tools.

In accordance with the present invention this locking means essentially comprises a pair of spirally wound springs 25 and 26 illustrated as formed of flat material, as is clearly shown in Figs. 4 and 5. These springs are preferably combined into a single continuous spring but are here'discussed as a pair for purposes of simplifying the explanation. Springs 25 and 25 are each coaxially positioned relative to shaft Ill, one .on either side of cam I5, thereby enveloping a portion of shaft I0. Preferably springs 25 and 25 are housed in suitable cuplike members or hubs 21 and 23, re-

spectively, one positioned on either side of cam ,as is clearly shown at 29' in Figs. and 7. With this construction it will be noted that by rotating hubs 2'! and 28 in opposite directions about the shaft [3, springs 25 and 26 may either be wound tightly against shaft It to prevent relative movement between shaft Ill and cam I5 or may, upon reverse rotation of hubs 2'! and 28 relative to each other, be unwound to release the gripping force exerted by their turns or convolutions upon shaft Ill and thus permit relative rotation between shaft I 0 and cam I5. In the particular instrumentation as illustrated in Figs. 2 and 4, clockwise rotation of hub 28 performs the locking operation.

It is desired that the cam I5 is normally locked or fixed with respect to tuning shaft I i! to prevent relative rotation between shaft I0 and cam I5. In connection with the present invention, therefore, it is desirable that means be provided which normally cause hubs 21 and 28 to be rotated in opposite directions about the shaft If] so as to cause the turns or convolutions of springs 25 and 26 to grip tightly shaft Ill, thereby preventing relative movement between shaft Ill and cam I5. To accomplish this there are provided ring members 30 and SI, respectively, associated with hubs 21 and 28. The ring member 30 comprises a ring portion which is adapted to be slipped over the hub 27 so as to be brazed or otherwise suitably fastened as indicated at 32, to an enlarged portion 21a of hub 21. Similarly the ring member 3| is arranged to be suitably fastened as indicated at 32 to an enlarged portion 28a of hub 28. Integrally connected to ring member 33 is an arm 3812 provided with a slot 351) which arm 30a extends in a direction parallel with the plane of cam [5. Also integrally connected with ring member 30 in substantially diametrically opposed relationship to arm 30b is a second arm 330 which is provided with a laterally projecting 7 portion 35d adapted to extend through an enlarged opening 33 in cam [5 so that the end thereof is on the opposite side of cam I5 from ring member 30. The portion 3311 is adapted to be positioned in the path of resetting prong 23 as will become apparent from the following description. Ring member 3I on the other hand also is provided with an arm 3Ia corresponding to arm 30a of ring member 30, which arm 3Ia is provided with a notched-out portion 3 lb. A second arm 3Ic integrally formed with ring member 3I and positioned in substantially diametrically opposed relationship with respect to arm 3 la includes a laterally projecting portion 3Id which is positioned so as to extend through an opening 34 in cam I5 which is very similar to the opening 33 mentioned above, but spaced therefrom in a manner clearly shown in Figs. 2 and 4. The laterally projecting portion 3Id of ring member-3| extends into the pathof movement of resetting prong 22.

In order to bias hubs 2'! and 28 to rotate in opposite directions to cause springs and 26 to frictionally engage or clamp tuning shaft IIJ,

arms a and'3 Ia of ring members 30 and 3| which extend on opposite sides of cam I 5,, are interconnected by a tension spring 35, the ends of which are hooked in notched-out portions 391) and 3Ib, respectively. An elongated opening 36 in cam I5 is provided to permit spring to interconnect arms 38a and 3I a which are on opposite sides of .cam I5. As is obvious from Figs. 1 and 3, spring 35 extends from one side of cam I5 to the other through opening 36.

With the arrangement described, spring 35 tends to cause rotation of hubs 21 and 28 in opposite directions about the shaft I0, hub 28.10- tating in a clockwise direction as viewed in Figs.

. 2 and 4 so that the turns or convolutions of springs 25 and 23 are caused tightly to grip shaft I0, thereby frictionally locking cam I5 to shaft I8.

.Relative movement between cam I5 and shaft II! including the lever assembly comprising levers I6 and II, by depressing push button It the cam I 5 is rotated to a predetermined position without resetting prongs 22 and 23 engaging with or moving the arms 35d and SM of ring members 30 and 3|, respectively. When, however, it is desired to setor reset the cam I5 relative to shaft II) to change the station setting or to initially establish a station setting, push button It is depressed to a greater extent than would normally be required for tuning the station whereby resetting prongs 22 and 23 engaging with arms 35d and 3 Id of ring members 30 and 3|, respectively, cause rotation of hubs 21 and 23 in opposite directions to effect I setting of shaft I0 is established by manually rotating shaft I0 through conventional tuning means, not shown, thelever It may be released, whereupon spring 35 will draw arms 30a and 3 la towards eachother to cause springs 25 and 26 again tightly to grip shaft III, thereby relocking cam I5 to shaft If! in this new position.

In order to prevent a possible inadvertent unlocking of the cam I5 relative to the shaft If], there may be provided an interference member 3i in the form of a rod eccentrically mounted as indicated at 38 in frame member II and extending for the full length of the tuning shaft 15. When member 3011. Further movement of lever the rod 31. is in the position shownin Fig. 2. the upper surface thereof acts as a stop for arm I611. of lever I5 so that pivotal movement of lever I6 beyond that required for movement of cam I5 to the proper position without unlocking cam I5 relative to shaft I is prevented. When stop 31 is rotated about eccentric axis 38, further pivotal movement of lever I6 is permitted whereby unlocking of cam I with respect to shaft Iii inthe manner described above can be obtained.

The operation of the selector unit I3a to rotate a corresponding control element such as cam I5 and thereby to rotate tuning shaft II) to a predetermined tuning position for the condenser I2 is apparent from the description above. In setting a cam I5 to an original predetermined position or resetting it to a subsequent predetermined position, the eccentric 3'I, if such an elementhas been provided, is moved from the posi-- tion shown in Fig. 2 so as not to interfere with further downward movement of lever I6. When the eccentric 31 is thus moved out of its interfering position, push button I4 is actuated to cause further clockwise rotation of lever I6 about the shaft I9 whereby resetting prong 22 engages member 3Id and resetting prong 23 engages I6 about the shaft I9 causes ring members 30 and 3| to be rotated .in opposite directions against the force of tension spring 35. Since ring members 30 and 3| are fastenedto hubs 21 and 28,

respectively, rotation of hubs 21 and 28 results. Furthermore, since the ends of spiral springs 25 and 26 are suitably fastened to hubs 2i and 28, spiral springs 25 and 26 are unwound so as no longer to frictionally grip shaft II) and shaft I0 is therefore free to move or rotate relative to cam I5 which is held stationary by the selector lunit. Accordingly, tuning shaft I0 and the associated condenser I2 are moved to a position corresponding to the desired tuning position which will be indicated by a suitable dial on the radio receiver not shown. When this predetermined tuning position has been obtained push button I4 is released and spring 35, acting through ring members .38 and SI causes rotation of spiral springs 25 and 26 in opposite directions so as to be wound tightly on shaft Ifl frictionally-engaging the same whereby cam I5 is locked to shaft Ill. Spring 24 causes lever I6 to return to its initial position when pressure is released from push button I4. The interference member 31 should be returned to the position shown in Fig. 2 following such an adjusting operation.

From the above description it is apparent that the present invention provides a simplified, sturdy, manually operable tuner for a radio receiver in which the tuning operations for initially setting or resetting the cam relative to the tuning shaft can be accomplished merely by actuating the push button device itself. Furthermore, a very positive arrangement for locking the cam or a plurality of them to the tuning shaft is provided, which locking arrangement of any desired cam is released in a simple manner. The area of frictional engagement of the locking means of the present invention is very large since a large number of turns may be provided for springs 25 and 26 without taking up any additional space in the radio receiver, thus providing full assurance that once the lockingfunction is performed relative movement between cam I5 and tuning shaft I0 cannot occur. In addition to the above advantages the present in- I vention provides for a very foolproof .construction. which i s mple to assemble and i e p n i to manufacture.

It will be apparent to those skilled in the art that the present invention is not limited to the particular construction shown, but various changes and modifications may be made without departing from the spirit and scope thereof, and it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the present invention.

I claim:

1. A control device for a radio receiver including a rotary tuning shaft, a cam mounted on said shaft for relative movement therewith, a pair of spirally wound spring means coaxially arranged with respect to said shaft and positioned one on either side of said cam with the ends adjacent to said cam fastened thereto, means for applying opposed rotary forces to the ends of said spring means not fastened to said cam to cause the turns of said spring means to grip said shaft and fixedly hold said shaft and cam as a unit, a selector unit for causing rotation of said cam and "tuning shaft as a unit, and means on said selector unit for applying reversed rotary opposed forces to the ends of said spring means not fastened to said cam so that said turns release their grip on said shaft whereby the position of said cam relative to said shaft may be varied.

2. A control device for a radio receiver including a rotary tuning shaft, a cam mounted on said shaft for relative movement therewith, a pair of spirally wound springs coaxially arranged with respect to said shaft and positioned one on either side of said cam with the ends adjacent to said cam fastened thereto, means for applying opposed rotary forces to the ends of said springs not fastened to said cam to cause the convolutions of said springs to grip said shaft and fixedly hold said shaft and cam as a unit, a selector structure for causing rotation of said cam and tuning shaft as a unit when operated in a predetermined manner, and means on said selector structure when operated in a different predetermined manner for applying reversed rotary opposed forces to the ends of said springs not fastened to said cam so that said convolutions are lunwound from said shaft to release their grip on said-shaft whereby the position of said cam relative to said shaft may be varied.

3. A control device for a radio receiver including a rotary tuning shaft, a cam mounted on said shaft for relative movement therewith, a pair of spirally wound springs coaxially arranged with respect to said shaft and positioned one on either side of 'said cam with the ends adjacent to said can! fastened thereto, a pair of reversely rotatable housing members one housing each of saidsprings, means for fastening the end not adjacent the cam of each of said springs to its associated housing member, spring means for biasing said housing members for opposite rotation about said shaft to cause the turns of said springs to grip said shaft and fixedly hold said shaft and cam as a unit, a selector structure including a first lever and a second lever operable to cause rotation of said cam and tuning shaft as a unit, and means on one of said levers when actuated in a predetermined manner to neutralize the effect of said spring means whereby said springs release their grip on said shaft so the position of said cam relative to said shaft may be varied 4. A control device fora radio receiver includshaft for relative movement therewith, a pair of spirally wound springs coaxially arranged with respect to said shaft and positioned one on either side of said cam with the'ends adjacent to said ing a rotary tuning shaft, a cam mounted on said cam fastened thereto, means for applying opposed rotary forces to the ends of said springs not fastened to said cam to cause the turns of said springs to grip said shaft and fixedly hold said shaft and cam as a unit, a selector structure comprising a finger actuated lever assembly for causing rotation of said cam and tuning shaft as a nalled in said frame, control means on said shaft including a cam, means for releasably holding said cam in a fixed position on said shaft comprising a pair of spirally wound springs enveloping said shaft, one positioned on each side of said cam and each having the end thereof adjacent said cam fastened to said cam, a first hub housing one of said springs and fastened to the end thereof not fastened to said cam, a second hub housing the other of said springs and fastened to the end thereof not fastened to said cam so that rotation in opposite directions of said hubs causes the convolutions of said springs tightly to grip said shaft while reverse rotation of said hubs causes said convolutions to unwind from said shaft, a first arm fastened to one of said hubs, a second arm fastened to the other of said hubs, a tension spring interconnecting said arms to bias said hubs in a direction to cause said convolutions to grip said shaft, manual means actuable to engage said cam to cause rotation of said cam and said shaft as a unit, a pair of release prongs associated with said manual means so that upon further actuation of said manual means said release prongs cause reverse rotation of said hubs with the unwinding of said convolutions from said shaft whereby relative movement between said cam and said shaft can be obtained.

6. A control device for a radio receiver including a rotary shaft, a cam mounted on said shaft for relative movement therewith, means enveloping a substantial length of said shaft for holding said cam in a predetermined fixed position on said shaft, a selector structure for causing rotation of said cam and said shaft as a unit, means on said selector structure for causing said first mentioned means to release said cam so that relative movement between said control unit and said shaft can be obtained, and rotatable means for preventing inadvertent operation of said last mentioned means.

7. Tuning apparatus for a radio receiver including a frame, a rotary control shaft journalled in said frame, control means on said shaft including a cam, means for releasably holding said cam in a fixed position on said shaft comprising a spirally wound spring enveloping said shaft and having one end thereof fastened to said cam, means for biasing said spring so that the spiral turns of said spring tightly grip said shaft to hold said cam in said fixed position relative to said shaft, manually actuable means for engaging said cam to cause rotation of said cam and said shaft, means associated with said manually actuable means for releasing said means for biasing said spring so as to cause said spiral turns to release their gripping action on said shaft whereby relative movement between said cam and said shaft can be obtained, and means eccentrically pivoted on said frame for preventing inadvertent operation of said means associated with said manually actuable means.

8. In a control device for controllable apparatus having a movable element therein and a control member adjustably mounted on said element, mechanism for operating said control member and releasably maintaining it in an adjusted position on said element including in combination a helical spring operatively connected with said control member and movable relative to said element to grip the same and to provide a member-holding force, and a selector unit having a pair of relatively pivoted portions with one portion operatively connectable with said spring to move the same to simultaneously release a holding force on said element and release said control member from said element, and having another portion operatively connectable with said member to hold the same against movement when the holding force is released and while said element is moved relative thereto.

9. In a control device for controllable apparatus having a movable element therein and a control member adjustably mounted on said element, mechanism for operating said control member and releasably maintaining it in an adjusted position on said element including in combination a helical spring on said element operatively connected with said control member and adapted selectively to grip said element or be released therefrom, and a pivoted selector unit having a pair of pivoted portions therein movable relatively to one another, with one of said portions being connectable with said member upon application of a pivotal pressure to said unit to move the same to a control position, and with the other portion upon further application of pressure to said unit being operatively connectable with said spring to move the spring in a manner to release the gripping pressure from said element.

10. In a control device for controllable apparatus having a movable element therein and a control member adjustably mounted on said element, mechanism for operating said control member and releasably holding it in an adjusted position on said element including in combination a pair of helical springs on said element with one on each side of said control member and operatively connected therewith to provide a holding force therefor, and a selector unit having one portion for moving said control member and another portion movable relative to said first portion and operatively connectable to said pair of springs to simultaneously move the same and release the holding force thereof.

11. In a control device for controllable apparatus having a movable element therein and a control member adjustably mounted on said element, mechanism for operating said control member and releasably holding it in an adjusted position on said element including in combination a pair of helical springs on said element movable in opposite directions thereon with one on each side of said control member and operatively connected therewith to provide a holding force therefor, structural means corresponding to each of said two springs and operatively connected therewith, and a selector unit having one iiportion for moving said control memberand another portion movable relative tosaid firstportion and connectable with said pair of structural means to simultaneously move the same and the springs therewith in opposite directions and, release. the holding force thereof.

12. In a control devicefor controlling apparatus having a movable element therein and a control member mounted on said element, the combination for operating said control member and releasably maintaining it in an adjusted position on said element including a spirally wound spring on. said, element operatively connected with, said control member for frictionally-holding .said control member in a fixed position on said element; a. selectorlunit for movingsaid member. and said element as a unit including an actuating means, and means on said actuating means and movable relative thereto for causing said spring to release from said element and permit relative movement. between said control member and said element. 7

13'. A control device for a radio receiver vhav- 12 ingiwamovable-element and a control memb-e thereon, the combination including a spirally wound spring associated with said element and operatively connected with said control member for holding: said control member in a fixed position on saidelement, and a selector unit having a-portion formoving said member and said element as a unit and having another portion movable relative to said first portion to operatively connect with said spring for causing said spring to release: said element from said member so that relative movement between said control member and said: element can be obtained.

ALEXANDER W. PLENSLER.

REFERENCES CITED The-following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,205,968 AJ-men; June 25, 1940 2,320,893 Schwarzet a1. June 1, 1943 

